Among semiconductor elements, power semiconductor elements for supplying power have a relatively large amount of heat generation. Therefore, as a substrate on which the power semiconductor element is mounted, a power module substrate including a circuit layer formed by bonding a first metal plate to one surface side of an insulating substrate made of, for example, AlN (aluminum nitride), Al2O3 (alumina), Si3N4 (silicon nitride) or the like, and a metal layer formed by bonding a second metal plate to the other surface side of the insulating substrate is used.
In such a power module substrate, a semiconductor element such as a power semiconductor element is mounted on the circuit layer through a solder material.
A heat sink for cooling a power module substrate is bonded to the other surface side of the metal layer.
For example, in PTL 1, a power module substrate is proposed obtained by using copper sheets used as a first metal plate and a second metal plate forming a circuit layer and a metal layer and directly bonding the copper sheets to an insulating substrate by a DBC method. In addition, as shown in a first view of PTL 1, a power module substrate with a heat sink is formed by bonding an aluminum heat sink to the power module substrate using an organic heat-resistant adhesive.
In addition, in PTL 2,a power module substrate is proposed using aluminum sheets as a first metal plate and a second metal plate forming a circuit layer and a metal layer. A power module substrate with a heat sink is formed by bonding a heat sink to the metal layer of the power module substrate by brazing.
Further, in PTL 3, a substrate is proposed in which a circuit layer is formed by bonding a metal plate to one surface of an insulating substrate and an aluminum heat sink is directly formed on the other surface of the insulating substrate by a casting method. As the metal plate forming the circuit layer, an aluminum sheet and copper sheet are used.